Multiplex_QA: A Quality Assessment Tool for STR Typing Data


Participants: David L. Duewer and John M. Butler


Project Timeframe: July 2003 to May 2006


Purpose: Multiplex_QA is a data analysis tool for visualizing short- and long-term changes in the performance of multiplexed electrophoretic assays, particularly the commercial short tandem repeat (STR) kits used by the human forensic identity community.  A number of quality metrics are calculated from the signal collected for the internal size standard included in nearly all multiplex assays.  These quality metrics are related to the signal intensity, symmetry, retention, resolution, and noise of data collected by capillary electrophoresis systems.  Interlocking graphical displays enable the identification of changes in the quality metrics with time, evaluation of relationships among the metrics, and detailed examination of electropherographic features of particularly interesting analyses.  While primarily intended for exploring which metrics are most useful for documenting data quality, the current version of the tool is sufficiently robust for use by forensic scientists with an interest in data analysis and access to a fast PC.


Progress: The software program, which runs in Excel, has been completed, a paper written describing its functionality, and a 127 page user manual prepared to enable its use. The software can be downloaded from



Publications or Presentations Resulting From This Project:

Duewer, D.L. and Butler, J.M. (2006) Multiplex_QA: an exploratory quality assessment tool for multiplexed electrophoretic assays. Electrophoresis 27: 3735-3746. (software available for download; User Manual - 127 pages - 3 Mb pdf file)


David Duewer demonstration and poster at NIJ DNA Grantees meeting (Washington, D.C.), June 28, 2005, "Multiplex_QA: An Exploratory Quality Assessment Tool for STR Multiplex Assays" [.pdf]


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Last updated: 06/19/2007


Disclaimer: This project was supported by National Institute of Justice Grant Number 2003-IJ-R-029, which is an interagency agreement between NIJ and the NIST Office of Law Enforcement Standards, awarded by the National Institute of Justice, Office of Justice Programs, US Department of Justice. Points of view in this document are those of the authors and do not necessarily represent the official position or policies of the US Department of Justice. Certain commercial equipment, instruments and materials are identified in order to specify experimental procedures as completely as possible.  In no case does such identification imply a recommendation or endorsement by the National Institute of Standards and Technology nor does it imply that any of the materials, instruments or equipment identified are necessarily the best available for the purpose.